To investigate whether breast-feeding protects children against rotavirus diarrhea (RVD), we compared rates of breast-feeding by age and enteric pathogens among 2276 children 0-4 years of age who attended a diarrhea hospital in Bangladesh. Infants 0-5 months were less likely to be breast-fed than children 6-11 months of age suggesting that some protection was associated with early breast-feeding. In every age group studied, breast-feeding was more common among children with RVD than those children with non-RVD whereas it was less common among children with cholera and shigellosis. Twenty percent of breast milks had high levels of neutralizing activity (greater than or equal to 320) to the human Wa strain of rotavirus but among infants less than 1 year, this activity did not appear to be protective since the 30 infants with RVD consumed milk whose titer did not differ significantly from 44 infants with diarrhea of other cause. Despite the prolonged breast-feeding which is common in Bangladesh, the mean age of hospitalization with RVD is approximately the same as in countries where the duration of breast-feeding is quite short. None of these 3 independent observations support a protective role for breast-feeding among children against rotavirus diarrhea after the first months of life.